Applying Body Mechanics to Octagonalisation

All of the legs for the staked worktable are now octagonalised, and I spent a couple of hours today making them pretty – final smoothing to remove a few spots of tearout, plenty of time with an eraser to remove stray pencil marks, and refining the fit of the tenons. Finalising the tenon size was a good opportunity to revisit the lathe and get a spot more turning practice in.

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The 50mm maxi-cut bit by Colt is a monster, and chewed through this oak rapidly while leaving a very clean finish and no splintering on the exit side.

When I originally turned the tenons I had been quite cautious and left them a touch oversized, which also abetted by wear to my “go block“, the corners of which had become burnished and slightly widened when checking the still-spinning tenons. So I prepared a new test mortice in some scrap oak left over from the Policeman’s Boot Bench, and took the barest shaving off each tenon until they all fitted smoothly without any slack. I also took the opportunity to clean up the shoulder of the tenon. Ideally I would like to turn a gentle cove into the shoulder, but my turning kit currently extends to one tool (the Easy Wood Rougher) and until I order the Easy Wood Finisher that particular shape is outside of my grasp. Instead, I made sure that the shoulder was clean and square to the tenon, with no stray bumps or unslightly catches.

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My standard grip for traversing boards and heavy stock removal is no good for octagonalisation – placing the off-hand on top of the bun raises the centre of gravity and encourages the plane to wobble during the stroke.

One of the advantages of performing a repetative task, such as octagonalising a set of four legs, is that it provides the opportunity to review technique and make incrimental changes towards efficiency. An aspect of woodwork that I find constantly interesting is the impact of body mechanics – the way that posture, including hand and foot placement in relation to the tool and the workpiece, will influence the outcome of a technique (for instance, cutting to a line, or planing a square and straight rabbet). Body mechanics have been a constant focus throughout my martial arts training, particularly when training with Clive, and that emphasis is something I find increasingly useful at the workbench. Octagonalisation is a case in point.

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This jointing grip helps hold the plane steady when removing the corner and establishing the facet. My fingers are pressed against the face of the leg to centre the plane on the aris of the workpiece.

When octagonalising the table legs, I found that my standard off-hand grip for planing wasn’t providing the control or comfort I wanted. Mainly this was because the initial strokes find the plane balanced on the aris of the workpiece, which makes holding the plane in a constant orientation to the leg difficult until the the facet is established. My standard grip works well for traversing boards with the jack plane, as it provides downward pressure to keep the plane in the cut, especially in ornery timber. But for octagonalisation it meant that the centre of gravity was too high and the plane was prone to wobbling.

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I transition to this grip once the facet has been established. Keeping the hand low to the plane body lowers the centre of gravity and keeps the plane in a constant orientation to the workpiece.

Instead, I established the facet by dropping my hand to the sole of the plane, mimicing the grip I use when jointing an edge – the thumb grips the side wall of the plane and the fingers curl under the sole to provide a fence to register against the workpiece. Once the corner is knocked off and the facet established, I shifted my thumb so that it was curled around the base of the bun while the fingers gripped the front edge of the bun – this kept the centre of gravity low for stability, but provided more power behind the plane stroke for rapid stock removal. After a few facets transitioning between these grips became second nature, providing a comfortable and precise way to carry out the operation.

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Four legs octagonalised, and made pretty. These are ready to be fitted to the sliding battens.

When I started octagonalising the legs I did not think much abut the plane grip I was using. Starting with a jointing grip, and transitioning between the two hand positions, occured insinctively in response to the feedback from the tool and the need to stabilise the plane on a narrow surface. Just as the projection of a plane iron is adjusted throughout a planing task (for instance, backing off for a finer cut as you near your layout lines), I would suggest that body mechanics are not static but also evolve throughout an operation in order to reflect to the changing state of the workpiece. I’m sure there are plenty of other examples of how body mechanics influence woodworking technique – I’ve previously written about how posture can contribute to effecive use rabbet planes and tongue and groove planes. But what are your favourite body mechanic tips for woodworking?

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